1. Field of the Invention
The present invention relates to a short-range photographic light source module and, more particularly, to a short-range photographic light source module for use in an image capture device.
2. Description of Related Art
The macro photography refers to a photographic mode for capturing an image of a short-range object or a very tiny object, typically produced at a reproduction ratio ranging from 1:1 to 1:4. Herein the ratio “1:4” means that the image size thus produced is a quarter of the actual object size. By reaching a reproduction ratio of 1:1, the actual size of the target object can be completely captured and presented. From the aspect of application, in addition to conventional applications in ecological observation and scientific research, the technique of macro photography can be more comprehensively utilized in various fields, including medical cosmetic surgery, criminal identification or anti-counterfeit verifications, such as fingerprint verification, paper bill anti-counterfeit authentication, and even identification of blood stains or body fluids by detection of fluorescent proteins present in body fluid and blood.
However, as the photographic distance further reduced, the aperture has to be set on a lower setting, thereby maintaining a sufficient depth of field to achieve a range of clearance for the target object. Meanwhile, with a small angle of view, light entering into the lens is at a low intensity level. Apparently, if the aperture is adjusted to be smaller, the intensity of light would get lower, resulting in darkness of the captured images which cannot be effectively analyzed or verified. To overcome this problem, one approach is to significantly extend the shutter open time. Unfortunately, in the case where the target object slightly moves or the image capture device itself sways during the shutter open time, the resulted image would become obscure or even completely unidentifiable. Another approach is to additionally install an external flashlight at the front end of the camera, so as to resolve this light insufficiency problem by means of light supplementation. But the flashlight can transiently provide light source only at the moment of shooting. Especially, for short-range photography, the control of exposure to light is very challenging and tends to cause the over-exposure or under-exposure problems. In such case, the pictures taken in this way may appear awkward and unnatural.
Furthermore, for specific target objects, such as a fingerprint left on a glass plate, light emitted by the flashlight and directly reflected from the glass plate may be much brighter than the fingerprint image itself and, thus, may entirely hinder the weak diffusion light from the fingerprint. Besides, for example, during an operation of searching for blood traces splashed on the ground in an area of intensive sunlight, the attempt to effectively identify the fluorescent reaction of blood traces by using a ultra-violet (UV) light source may fail due to strong UV emission in sunlight which seriously deteriorates the quality of images. Consequently, issues concerning how to adequately illuminate the image area intended to be captured, to provide accurate light supplementation at a selected angle without the occurrence of over-exposure, and even to arbitrarily choose a suitable light source of light supplementation to achieve an expected shadow effect to thereby enhance the three-dimensional perception of the target object, are to be effectively resolved by the short-range photographic light source module according to the invention.
On the other hand, in the case of money authenticity verification, for example, some hidden anti-counterfeit mechanisms need be magnified and verified with visible light, while the remained fluorescent anti-counterfeit mechanisms should be illuminated by UV light. For the situation where two different types of light sources are required for photography in one occasion, the two types of external light sources have to be switched frequently to capture different types of images of the target object. This not only forces the user to prepare two different types of light sources at the same time, but causes alignment problem in the captured picture due to light source alternations during a photographic operation. Hence, the aforementioned issues are also to be addressed by the invention.